We at @effi have been using CryptPad self hosted for years. The functionalities fulfill our needs as does high level of data security.
The only nuisance has been use with Firefox-based browsers: apparenty in the case of HC nerd users (like us) who don't boot their OS (because there's really no need for that using GNU/Linux as often as with the M$ OS) and have also the browser on for months, there seems to be something left or stuck that occasionally leaves login to CryptPad to wait forever.
But hey - it is a good reason for closing your browser every month or so. :P
CryptPad is the only really secure groupwork sw I am aware of. I recommend it and that is quite a lot from a critical motormouth like me. :P